Determination of anisotropic dipole moments in self-assembled quantum dots using Rabi oscillations

By investigating the polarization-dependent Rabi oscillations using photoluminescence spectroscopy, we determined the respective transition dipole moments of the two excited excitonic states |Ex> and |Ey> of a single self-assembled quantum dot that are nondegenerate due to shape anisotropy. We find that the ratio of the two dipole moments is close to the physical elongation ratio of the quantum dot.Comment: 11 pages, 2 figures, MS Word generated PDF fil

Quantum speed limit for relativistic spin-0 and spin-1 bosons on commutative and noncommutative planes

Quantum speed limits of relativistic charged spin-0 and spin-1 bosons in the background of a homogeneous magnetic field are studied on both commutative and oncommutative planes. We show that, on the commutative plane, the average speeds of wave packets along the radial direction during the interval in which a quantum state evolving from an initial state to the orthogonal final one can not exceed the speed of light, regardless of the intensities of the magnetic field. However, due to the noncommutativity, the average speeds of the wave packets on noncommutative plane will exceed the speed of light in vacuum provided the intensity of the magnetic field is strong enough. It is a clear signature of violating Lorentz invariance in quantum mechanics region.Comment: 8 pages, no figures. arXiv admin note: text overlap with arXiv:1702.0316

Global Hot Gas in and around the Galaxy

The hot interstellar medium traces the stellar feedback and its role in regulating the eco-system of the Galaxy. I review recent progress in understanding the medium, based largely on X-ray absorption line spectroscopy, complemented by X-ray emission and far-UV OVI absorption measurements. These observations enable us for the first time to characterize the global spatial, thermal, chemical, and kinematic properties of the medium. The results are generally consistent with what have been inferred from X-ray imaging of nearby galaxies similar to the Galaxy. It is clear that diffuse soft X-ray emitting/absorbing gas with a characteristic temperature of $\sim 10^6$ K resides primarily in and around the Galactic disk and bulge. In the solar neighborhood, for example, this gas has a characteristic vertical scale height of $\sim 1$ kpc. This conclusion does not exclude the presence of a larger-scale, probably much hotter, and lower density circum-Galactic hot medium, which is required to explain observations of various high-velocity clouds. This hot medium may be a natural product of the stellar feedback in the context of the galaxy formation and evolution.Comment: 11 pages, invited talk in the workshop "The Local Bubble and Beyond II

Numerical simulation of two-phase cross flow in the gas diffusion layer microstructure of proton exchange membrane fuel cells

The cross flow in the under-land gas diffusion layer (GDL) between 2 adjacent channels plays an important role on water transport in proton exchange membrane fuel cell. A 3-dimensional (3D) two-phase model that is based on volume of fluid is developed to study the liquid water-air cross flow within the GDL between 2 adjacent channels. By considering the detailed GDL microstructures, various types of air-water cross flows are investigated by 3D numerical simulation. Liquid water at 4 locations is studied, including droplets at the GDL surface and liquid at the GDL-catalyst layer interface. It is found that the water droplet at the higher-pressure channel corner is easier to be removed by cross flow compared with droplets at other locations. Large pressure difference Δp facilitates the faster water removal from the higher-pressure channel. The contact angle of the GDL fiber is the key parameter that determines the cross flow of the droplet in the higher-pressure channel. It is observed that the droplet in the higher-pressure channel is difficult to flow through the hydrophobic GDL. Numerical simulations are also performed to investigate the water emerging process from different pores of the GDL bottom. It is found that the amount of liquid water removed by cross flow mainly depends on the pore's location, and the water under the land is removed entirely into the lower-pressure channel by cross flow

Incidence of advanced cutaneous malignant melanoma in the UK: a systematic review

Objectives: Cutaneous melanoma (CM) is one of the most aggressive forms of skin cancer. In 2008, CM was found to be the sixth most common cancer in the UK. The aim of this review was to systematically identify patients with advanced CM, limited to stage IIIc and stage IV disease. Methods: Literature searches were undertaken in the Cochrane Library, MEDLINE, CINAHL and EMBASE between December 2010 and March 2011. Webpages of the Office of National Statistics, Cancer Research UK and the Welsh Cancer Intelligence and Surveillance Unit were also scanned. A narrative synthesis was undertaken due to the heterogeneity of included studies. Results: Three observational studies were identified. One study was in East Anglia, England while the remaining two were in Scotland. Both studies in Scotland estimated that 2% of all melanoma patients had advanced CM at the time of diagnosis. It was also noted that, in East Anglia, the incidence of stage IV CM decreased from 0.42 to 0.13 per 100,000 population per year between 1991 and 2004. The review highlighted the challenges in identifying patients with advanced CM from available data. Conclusions: This review highlighted the lack of, and the need for primary studies to estimate the incidence of advanced CM in the UK. Defining this subgroup of patients is important for identifying patients for targeted treatment. We suggest that researchers must clearly define this population of patients in future studies